A man has been charged in connection with the investigation into the so-called Punish A Muslim Day letters, West Yorkshire Police said.
David Parnham, 35, is accused of 14 offences including one count of soliciting to murder.
He is also charged with two counts of sending a number of letters promoting a 'Punish A Muslim Day', encouraging the commission of one or more of a number of offences.
Parnham further faces five counts of sending a substance with the intention of inducing in a person a belief that it is likely to contain a noxious substance, five counts of sending a number of letters conveying a threat and one count of making a bomb hoax.
The man, from Lincoln, is due to appear at Westminster Magistrates' Court on Friday.
Parnham was arrested on Tuesday by counter-terrorism police as part of an intelligence operation.
A residential property and office building in Lincoln city centre were searched.